Developing a preventive pruning program in your community

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Urban Forest Hurricane Recovery Program
http//treesandhurricanes.ifas.ufl.edu
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Developing a preventive pruning program in your
community Young trees

• Dr. Ed Gilman and Traci Jo Partin

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Pruning can reduce damage

• A recent study at UF showed that pruning reduces
  the angle of trunk bend when trees are exposed to
  high winds.

Not pruned
Reduction pruning
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Preventive Pruning young trees

• Set objectives
• Determine pruning cycle and dose
• Execute pruning plan- make good cuts-
  prioritize trees with structural issues-
  temporary vs. permanent branch management

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Poor form
Good form

• Principles of strong structure
• One dominant trunk
• Strong branch unions
• Balanced canopy

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Objective Reduce structural issues that cause
tree failure

• Codominant stems stems of equal size
  originating from the same point on the tree
• Included bark bark pinched between two stems,
  indicating a weak union
• Unbalanced canopyone side much heavier, or most
  weight at the tips of branches
• Large low branches

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Strong connection
Collar
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Weak structure codominant stems and bark
inclusions
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Codominant stems often cause branch failure in
storms
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Failure due to bark inclusion
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Unbalanced canopy

• Lions-tailing trees with foliage concentrated at
  the tips of branches because inner branches were
  removed.
• More susceptible to hurricane damage
• Difficult to restore

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Lions-tailed trees failed
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Nothing to cut back to should the tree be storm
damaged.
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Notice the large limbs located close to the
ground these will eventually have to be removed
for clearance.
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Big cuts can result in decay and cracks.
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Low and big cuts can be avoided with early
pruning.
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Objective Prune to promote strong structure
Trees require about 25 years of training to
develop strong structure.

• Structural Pruning Strategies
• Develop or maintain a dominant leader
• Identify lowest branch in the permanent canopy
• 3. Prevent branches below the permanent canopy
  from growing too large
• 4. Space main branches along dominant trunk
• Keep all branches less than ½ the trunk diameter
• Suppress growth on branches with included bark

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Preventive Pruning young trees

• Set objectives
• Determine pruning cycle and dose
• Execute pruning plan- make good cuts-
  prioritize trees with structural issues-
  temporary vs. permanent branch management

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Pruning cycle the interval or time between each
pruning event

• Depends on quality of nursery stock, growth rate,
  climate, and species.
• Should be shorter in warmer climates where trees
  grow faster.
• A longer pruning cycle can lead to larger cuts
  having to be made to correct structural issues.

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Determine a pruning cycle

• Pruning cycle - more than 3-5 years higher
  pruning dose- every 1-2 years smaller pruning
  dose
• Suggested program
• - At planting- Year two or three- Year five or
  six- Year ten- Year fifteen

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Pruning dose the amount of live tissue removed
at one pruning

• Depends on customer expectations, the size of the
  stems, and the pruning cycle.

Low pruning dose ( lt than 20) Higher pruning dose ( gt than 20)
Mature or recently planted trees Young, established trees
Cooler climates with short growing season Warm climates where trees have longer growing season
Decay prone species Good compartmentalizers
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Appropriate Pruning Dose for Specific Applications Appropriate Pruning Dose for Specific Applications
Large Pruning Dose Small Pruning Dose
Municipality Residences, commercial properties
Long pruning cycle Short pruning cycle
Aesthetics of less concern Aesthetics are a concern
Effects on the Tree from Applying Pruning Doses Effects on the Tree from Applying Pruning Doses
Large Pruning Dose Small Pruning Dose
Larger pruning wounds Smaller pruning wounds
Larger void in canopy Smaller void in canopy
Greatly encourages growth in unpruned portions of tree Encourages some growth in unpruned portions of the tree
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Impact of pruning dose on co-dominant stem
growth
before
after 75 dose
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Impact of pruning dose on co-dominant stem
growth
Foliage removed for 75 dose
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Maximum critical diameter the largest diameter
pruning cut you are willing to make on a certain
species

• This limit should be set for both removal and
  reduction cuts.
• Should be smaller for decay-prone species.
• Is controlled by the pruning cycle

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Branch size - proportion relative to trunk
- actual diameter of stem
Branch size Consequences of Removal Recommended Action
Less than ½ trunk diameter Few consequences Remove if needed
1/3 to ½ trunk diameter Some trunk defects could result Consider shortening instead
More than ½ trunk diameter Defects likely Shorten instead of removing
Large enough to have heartwood Defects likely Shorten instead of removing
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Preventive Pruning young trees

• Set objectives
• Determine pruning cycle and dose
• Execute pruning plan- make good cuts-
  prioritize trees with structural issues-
  temporary vs. permanent branch management

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Types of pruning cuts

• Reduction cut shortens the length of a stem by
  pruning back to a smaller limb.
• Removal cut prunes a branch back to the trunk or
  parent branch.

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Make good pruning cuts

• Step 1
• Make an undercut about 12 inches from the trunk.
• Step 2
• Make a topcut farther out on the limb.
• Step 3
• Remove the stub with final cut, being careful not
  to cut flush against the trunk. Leave the collar
  intact.

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Branch bark ridge
Collar
Collar swollen area at the base of the branch
where it joins the trunk. The tissue is rich in
energy reserves and chemicals that hinder the
spread of decay. Good pruning cuts avoid cutting
into the collar.
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Bad cut- called a flush cut
Wound wood does not develop evenly.
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Reduction cut
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Pruning strategies

• Execution
• Prioritize which trees to prune
• Decide location of lowest permanent
  limbtemporary branch management vs. permanent
  branch management

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Prioritize Structural pruning not as important
on these
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Temporary vs. permanent branch management

• Keep in mind that all branches will eventually be
  removed on trees less than 4 caliper

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Temporary vs. permanent branch management
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Pruning Plan First 5 years

• Most branches are temporary.
• Do not remove more than 35 of live foliage at a
  pruning visit.
• Reduce all branches greater than ½ trunk
  diameter.
• Reduce and/or remove all branches or stems
  competing with the one selected to be the leader.
• Reduce and/or remove large, low vigorous
  branches.
• Remove broken, cracked or severely damaged
  branches.

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Reduce growth rate of low aggressive branches
Push
Push
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Before
After
Pushback
Year two
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After
Before

• Structural pruning is a three step process
• Identify the stem that will make the best leader.
• Identify which stems are competing with this
  leader.
• Decide where to shorten these competing stems.

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After
Before
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Pruning Plan 5 20 years

• Do not remove more than 25-35 of live foliage.
• Reduce all branches greater than ½ trunk
  diameter.
• Identify lowest scaffold limbs of the permanent
  canopy and reduce all aggressive lower branches.
• Reduce branches with included bark.
• Reduce or remove competing leaders (if there are
  more than 3 competing leaders, this can be done
  in stages).
• Reduce branches within 18 of largest limbs.

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Before
After
Push
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Two years later
Before
after
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Before
After
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Dominant leader structure after two pruning visits
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Before pruning
After pruning
Transforming a bush into a tree
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Two years later
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Pruning Plan 20 30 years

• Identify 5 to 10 permanent scaffold limbs and
  reduce branches within 18-36 to avoid clustered
  branches.
• Space permanent scaffold limbs to reduce wind
  resistance.
• Remove many or all of the branches below the
  first permanent limb.
• Reduce branches with included bark.
• Reduce and/or remove competing leaders.

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Reduce growth on branches below permanent canopy
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After
2 years later
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before
after
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Here is a tree that was damaged in a storm. As a
result, many stems are growing upright
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Remove two upright, interior stems
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After removing right codominant stem
Before
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Before - year 8
After
Debris
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Before - year 8
One year after pruning
After
Debris
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Before - year 8
One year after pruning
18 months after pruning
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With dedication to a management plan, your
community can become a model for others